Brain tumors (astrocytomas or gliomas) represent the leading cause of cancer-related death in children and the fourth leading cause in adults. While there have been considerable advances in our ability to partially arrest their growth by targeting the genetic and molecular changes within cancer cells, a substantial number of patients with gliomas succumb to their disease, develop secondary brain dysfunction as a result of treatment, or fail to regain normal neurologic function despite treatment. We hypothesize that improved patient outcome from brain tumor treatment requires that therapies consider the bi-directional interactions between neoplastic cells and non-neoplastic cells in the tumor surround. Over the past five years, we have developed and validated several genetically-engineered mouse models (GEMMs) of low-grade glioma that recapitulate the salient features of the human condition. In this application, we will exploit these accurate GEMM systems to understand (1) the role of the tumor microenvironment, including important immune system cells, in gliomagenesis and tumor growth, (2) the effects of glioma growth on normal neuronal function, and (3) the secondary effects of chemotherapy and radiation therapy on non-neoplastic brain cells. Using a cross-disciplinary approach, we aim to unravel the cellular and molecular determinants that underlie the bi-directional interactions between neoplastic cells and non-neoplastic cells in low-grade glioma, and use these insights to identify novel strategies aimed at improving the outcome of patients with these cancers. To this end, we have assembled a new team of investigators with prior involvement in large-scale cooperative research initiatives and expertise in mouse model generation (Dr. David Gutmann), stromal interactions in brain tumors (Drs. David Gutmann, Joshua Rubin), advanced small-animal imaging (Dr. Joel Garbow), genomic influences on tumorigenesis (Dr. Karlyne Reilly), and multi-modality imaging (Dr. Mark Ellisman). Finally, we have individually leveraged the rich research environments at Washington University, University of California-San Diego, and The National Cancer Institute to tackle this complex problem in cancer biology.